The present invention relates to tank pressure control apparatus, and particularly to valve apparatus which operates to seal the vapor space in the interior of a fuel tank during refueling and reopens at some point after refueling has been completed to vent the vapor space. More particularly, the present invention relates to a tank pressure control apparatus having a float valve movable to close a venting outlet in a fuel tank during refueling and a device for assisting in moving the float valve to a venting outlet-opening position after refueling has been completed.
Vehicle fuel systems are known to include pressure-relief valves mountable on either fuel tanks or filler necks. These conventional valves are not equipped to regulate the volume of fuel introduced into the vehicle fuel system during refueling. Although fuel pump nozzles are known to include sensor means for shutting off the flow of fuel from the nozzle when the fuel tank is nearly filled, it has been observed that users frequently manually override or bypass such fill-limiting sensors by continuing to pump fuel after the pump nozzle has automatically shut off several times. It will be appreciated that such unauthorized refueling practices can result in overfilling the fuel tank which can effectively reduce the fuel vapor expansion capacity available within the filled fuel tank.
An improved tank pressure control system is provided for maintaining a head pressure within the fuel tank which exceeds the maximum head pressure that can develop in the filler neck due to filling the filler neck with fuel. The improved control system advantageously aids in preventing fuel pump operators from overfilling fuel tanks by providing a pressurized fuel vapor barrier within the fuel tank that acts to block the introduction of fuel into the fuel tank in excess of a predetermined fuel capacity during refueling.
At the same time, the improved system is adapted to release fuel vapor in periods other than during refueling to increase the flow of fuel vapor to, for example, the atmosphere under the control of a pressure-relief fuel cap or the like. Such a timely release of fuel vapor from the fuel tank minimizes the risk that an excessive pressure buildup will occur in the tank during vehicle operation and drive a surge of liquid fuel through the filler neck to impinge the fuel cap and thereby avoid shortcomings of known fuel tank pressure control systems.
One object of the present invention is to provide a tank pressure control apparatus that closes a tank venting outlet during refueling to control the amount of fuel that can be introduced into the fuel tank and reopens after refueling has been completed to permit generally unrestricted venting of the fuel tank under the control of a pressure-vacuum relief valve mounted on the filler neck fuel cap or elsewhere.
Another object of the present invention is to provide a tank pressure control apparatus that includes a float valve supported for movement in the fuel tank to close a tank-venting outlet during refueling and a device for assisting in positively moving the float valve away from its tank vent-closing position after refueling has been completed in response to exposure of the device to either an external force generated during operation or movement of the vehicle after refueling or a pressure differential developed around the device after refueling whether the vehicle is being operated or not.
Yet another object of the present invention is to provide a tank pressure control valve assembly that is configured to close a tank venting outlet in the event that an attempt is made to put more fuel into a full or nearly full fuel tank to ensure that a user cannot inadvertently or deliberately overfill the fuel tank.
According to the present invention, an apparatus is provided for controlling discharge of fuel vapor from a fuel tank having a filler neck during refueling. The apparatus includes a valve housing mounted in a wall of the fuel tank and formed to include a venting outlet coupled by hose means to the filler neck. The apparatus includes closing means provided in the valve housing for closing the venting outlet in response to filling the fuel tank to a predetermined level. The closing means includes a float valve formed to include an outlet closing portion and an interior chamber configured to retain air or fuel vapor therein so that the float valve is buoyantly supported in liquid fuel which is admitted into the valve housing during refueling. The float valve is also formed to include an aperture providing an opening into the interior chamber.
The apparatus further includes a device for controlling discharge of air or fuel vapor from the interior chamber in the float valve through the aperture. The device is normally positioned to close the aperture in the float valve so that air and fuel vapor is retained in the interior chamber thereof to provide the float valve with sufficient buoyancy to float in liquid fuel admitted into the valve housing. Thus, the float valve is able to float in liquid fuel to its outlet-closing position during refueling. The device is movable to a position uncovering the aperture to release pressurized air or fuel vapor contained in the interior chamber causing the float valve to become less buoyant and sink to a venting outlet-opening position. Such movement only occurs after refueling has been completed. In certain embodiments, the device is moved in response to external forces generated during operation or movement of the vehicle carrying the fuel tank. In other embodiments, the device is moved upon exposure to a pressure differential developed around the device whether the vehicle is stationary or in motion.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.